1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device and a method of fabricating the same, and more particularly, to an LCD device that may prevent light in adjacent pixel regions from being mixed to prevent picture quality from deteriorating, and a method of fabricating the same.
2. Discussion of the Related Art
Because of increased visual presentation of information, display devices have received much attention. Accordingly, various kinds of competitive display devices have been researched and developed. To gain a large market share, it is necessary for a display device to have the advantageous properties of the low power consumption, thin profile, light weight, and good picture quality.
In the past, a cathode ray tube (CRT) was widely used. However, the CRT is not thin nor light weight as desired today. Accordingly, many efforts have been made to develop various flat display devices that can substitute for the CRT. Among the various flat display devices, a liquid crystal display (LCD) device has attracted much attention due to it performance and ease of mass production. Thus, the LCD device is widely used in various fields from television to navigation systems.
Generally, the LCD device has liquid crystal cells arranged in a matrix. A data signal is individually provided to each liquid crystal cell, to thereby control the light transmittance of the liquid crystal cell. As a result, a desired image is displayed on the LCD device.
The LCD device includes an LCD panel, wherein the LCD panel includes a thin film transistor array substrate, a color filter substrate, and a liquid crystal layer formed between the two substrates.
Hereinafter, a related art LCD device will be described with reference to FIG. 1.
FIG. 1 illustrates a structure of a related art LCD device. As shown in FIG. 1, the related art LCD device includes an upper color filter substrate, a lower thin film transistor array substrate 101, and a liquid crystal layer 109.
The color filter substrate includes a color filter 117 formed on a substrate 113, a black matrix (BM) 115 formed between each color filter 117, and a common electrode 111 formed on the color filter 117 and the black matrix 115.
The thin film transistor array substrate 101 includes a pixel electrode 107 formed in each pixel region (P) of a substrate, a thin film transistor (TFT) that functions as a switching element, and array lines 103 and 105. The thin film transistor (TFT) is formed in each pixel region (P) defined by gate and data lines 103 and 105 formed substantially perpendicular to one another. In the pixel region (P), the pixel electrode 107 is formed of a transparent conductive layer.
The liquid crystal layer 109 is formed between the thin film transistor array substrate 101 and the color filter substrate, wherein the liquid crystal layer 109 is formed of liquid crystal having a refractive anisotropy.
Although not shown in FIG. 1, polarizing sheets are formed on outer surfaces of the LCD panel. Then, a backlight unit including a lamp and optical sheets is below the polarizing sheet of the lower substrate. Below the polarizing sheet formed on the lower surface of the lower substrate, there are top and bottom cases to support the LCD panel.
FIG. 2 is a cross sectional view illustrating a related art LCD panel. FIG. 3 is an enlarged cross sectional view illustrating a color filter substrate of an LCD panel shown in FIG. 2.
As shown in FIG. 2, the polarizing sheets 119a and 119b are formed on the lower surface of the thin film transistor array substrate 101 and on the upper surface of the color filter substrate 113. FIG. 2 shows only one pixel region (P). The LCD panel includes a plurality of pixel regions (P), as explained in FIG. 1. Although not shown in FIG. 2, the liquid crystal layer is formed by liquid crystal between the pixel electrode 107 and the common electrode 111.
As shown in FIG. 3, the color filter substrate 113 includes the black matrix 115 of metal or black resin formed along the circumstance of the pixel region, and the color filters of red (R), green (G) and blue (B) 117a, 117b and 117c sequentially and repeatedly formed between each black matrix 115. Then, an overcoat layer 112 is formed on the color filters 117a, 117b and 117c, and the common electrode 111 is formed on the overcoat layer 112. At this time, the common electrode 111 is formed of a transparent conductive layer, for example, Indium Tin Oxide (ITO). Then, the polarizing sheet 119a is formed on the lower surface of the color filter substrate.
A method of fabricating the above-mentioned color filter substrate will be explained with reference to FIGS. 4A to 4E. The color filter substrate is formed by using a pigment dispersion method having high color-realization properties.
As shown in FIG. 4A, the metal material or black resin, which can block the light, is formed on the entire surface of the substrate 113 and is then etched by photolithography, thereby forming the pattern of black matrix 115. When liquid crystal molecules are abnormally aligned due to distorted electric fields, the light may leak. The black matrix prevents light from leaking and also prevents a photocurrent from occurring due to light being incident on a channel region of the thin film transistor.
As shown in FIG. 4B, the entire surface of the substrate 113 including the black matrix 115 is coated with a color resist layer 116 of any one color of red, green and blue colors, for example, a red-color resist material by a spin-coating method, whereby a red-color resist layer 116 is formed on the substrate 113. After aligning a photo-mask 114 above the red-color resist layer 116 of the substrate 113, the exposure process is performed thereto. Thereafter, when developing the red-color resist layer 116, the portions-exposed to the light are left and the other portions unexposed to the light are removed, as shown in FIG. 4C, due to the negative development properties of the red-color resist layer 116, whereby the red color filter pattern 117a is formed. Then, the red color filter pattern 117a is cured. By repeatedly performing the above-mentioned process for the green-color resist and the blue-color resist, as shown in FIG. 4D, the green and blue color filter patterns 117b and 117c are formed, and the overcoat layer 112 and the common electrode 111 are formed.
The green and blue color filter patterns 117b and 117c are formed in the same method as that of the red color filter pattern 117a. Then, a transparent conductive material, for example, Indium Tin Oxide (ITO) or Indium Zinc Oxide (IZO), is formed on the entire surface of the substrate including the red, green and blue color filter patterns 117a, 117b and 117c and is then patterned by photolithography, thereby forming the common electrode 111. In this case, the overcoat layer 112 of BenzoCycloButene (BCB) is formed between the common electrode 111 and the color filter patterns 117a, 117b and 117c, to thereby protect the color filter patterns 117a, 117b and 117c and to compensate for the step coverage between the common electrode 111 and the color filter patterns 117a, 117b and 117c. 
Subsequently, as shown in FIG. 4E, the polarizing sheet 119a is adhered onto the lower surface of the color filter substrate. The polarizing sheets 119a and 119b adhered onto the color filter substrate and the thin film transistor array substrate control the transmittance of light emitted from the backlight unit.
For the LCD panel fabricated by the related art, each pixel region is independently driven by its thin film transistor that functions as a switching element. Also, the black matrix is provided between each of the pixel regions, whereby each pixel may independently display the corresponding color.
However, the transmitted light may be mixed in the adjacent pixel regions of the related art LCD device, whereby the color purity of unit pixel region deteriorates due to the mixed light.